Or pat-downs and bag searches at park entrances, festival gates and holiday events?

Although resorting to such measures would be a "shame," Nickels said, he would not rule them out during a Monday news conference to announce his prohibition of concealed weapons on city property.

"We do hope that our parks and our Seattle Center events remain open and accessible and welcoming to all," Nickels said. "But we will also make sure that they're safe."

Nor is it yet clear whether Nickels' move will land the city in court -- with gun rights activists contending the mayor has violated state law. "I certainly would not be surprised if there is a challenge to our authority on this," Nickels acknowledged. Still, "We believe we do have the authority."

Nickels has directed that firearms and other "dangerous weapons" be banned from Seattle facilities. Private organizers using city land for events such as Bumbershoot also will be responsible for enforcing the prohibition. The move comes after a shooting last month that injured three people during a festival at Seattle Center.

"People with concealed weapons will be asked to leave or to hand over their gun," he said. Under Washington law, "we would not be able to throw them in jail or fine them."

Still, critics say the move violates state law and the rights of legally authorized gun owners. Washington's statute prohibits local governments from enacting gun laws that are stricter than state codes.

"The gun rights community, the people I've been talking to all day long, think that he's way over the fence on this one," said Dave Workman, senior editor for Gun Week magazine, a periodical owned by the Bellevue-based Second Amendment Foundation. "He's exceeding his authority and he's trying to enter into an area that the Legislature has the sole authority on."

But city officials say they have the same authority to ban guns as other landowners.

"I wouldn't quite say there is a constitutional right to carry a gun at every city-sponsored event or in many buildings that already exist throughout the state," Police Chief Gil Kerlikowske said.

Nickels contends a 2006 state Supreme Court ruling bolsters his standing. In the case, a private gun show organizer sued the city of Sequim for imposing restrictions on firearm sales at an event at the city convention center. The high court ultimately held that the state pre-emption law does not prohibit municipal property owners from imposing firearms conditions similar to those established by private property owners, said officials with the Washington Attorney General's office.

Also, state statutes specifically allow municipalities and local jurisdictions to restrict gun possession within city-owned stadiums and convention centers. And the Supreme Court has also upheld other local firearms rules, such as workplace restrictions, where the city is acting as an employer, the Attorney General's office said.

The question of whether Nickels' order is legally defensible would likely rest on whether it crosses a line from the administration of municipal affairs into a policy excessively directed at the general public, added Eric Nelson, an assistant state attorney general.

"It's an interesting question as to how far can the city stretch these principles to the extent that activates in parks and community centers are not rules of general application that are subject to the pre-emption," Nelson said. "It's going to be a question of fairly nuanced line-drawing; that's my view."

Over the next 30 days, Seattle police, attorneys and city department heads will work out how they will enforce the policy, Nickels said. "I would hope we don't have to put metal detectors in all of our public buildings. That would be a shame," he said. "We will start with reasonable measures. And we will work from there to make sure that these rules are enforced."

"This is a small step and I hope not the last step in protecting our public from gun violence," he said.

One evening last month, a 22-year-old Snohomish County man allegedly tried to draw a gun from an ankle holster during an altercation at the Northwest Folklife Festival. Clinton Grainger's gun discharged during the struggle with another man, authorities say. A single bullet injured one man's nose, passed through another person's hand and lodged in a woman's leg. Grainger carried a concealed pistol license despite a history of mental illness.

Nickels also plans to again lobby the Legislature this winter to take measures aimed at keeping guns out of the hands of the mentally ill, felons and children, he said Monday.

Two years ago, Nickels and Kerlikowske helped lead an unsuccessful campaign to adopt stricter state regulations requiring background checks on private sales at gun shows. The measure died in the Legislature in the face of opposition from gun rights groups.

Nickels also hopes state lawmakers will grant cities and other local governments authority to "protect your people as you see fit," he said.

Because Nickels' directive is an executive order issued directly to city departments, it does not require City Council approval. Still, several council members said Monday that they support the mayor's order.

"It's a positive move in the right direction," said Councilman Tim Burgess, chairman of the public safety committee.

"It will give clear notice that weapons and firearms are not permitted," added Councilman Tom Rasmussen, chairman of the council's parks committee. "It gives the city a tool or a means to take action against someone who violates that.

"It's highly unlikely we're going to be posting metal detectors or having pat-downs at the entrances of our parks. I wouldn't support (that) and I don't think we're going to get to that point."